Space

Planet X Projected at Solar System's Edge

admin@mysteriesunsealed.com — Sat, 01 Mar 2008 21:35:30 GMT

"Scientists at a Japanese university said Thursday they believed another planet up to two-thirds the size of the Earth was orbiting in the far reaches of the solar system.

The researchers at Kobe University in western Japan said calculations using computer simulations led them to conclude it was only a matter of time before the mysterious "Planet X" was found.

"Because of the very cold temperature, its surface would be covered with ice, icy ammonia and methane," Kobe University professor Tadashi Mukai, the lead researcher, told AFP.

The study by Mukai and researcher Patryk Lykawka will be published in the April issue of the Astronomical Journal.

"The possibility is high that a yet unknown, planet-class celestial body, measuring 30 percent to 70 percent of the Earth's mass, exists in the outer edges of the solar system," said a summary of the research released by Kobe University.

"If research is conducted on a wide scale, the planet is likely to be discovered in less than 10 years," it said.

Planet X--so called by scientists as it is yet unfound--would have an oblong elliptical solar orbit and circle the sun every thousand years, the team said, estimating its radius was 15 to 26 billion kilometers.

The study comes two years after school textbooks had to be rewritten when Pluto was booted out of the list of planets.

Pluto was discovered by the American astronomer Clyde Tombaugh in 1930 in the so-called Kuiper belt, a chain of icy debris in the outer reaches of the solar system.

In 2006, nearly a decade after Tombaugh's death, the International Astronomical Union ruled the celestial body was merely a dwarf planet in the cluttered Kuiper belt.

The astronomers said Pluto's oblong orbit overlapped with that of Neptune, excluding it from being a planet. It defined the solar system as consisting solely of the classical set of Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.

The team noted that more than 1,100 celestial bodies have been found in the outer reaches of the solar system since the mid-1990s.

"But it would be the first time to discover a celestial body of this size, which is much larger than Pluto," Mukai said.

The researchers set up a theoretical model looking at how the remote area of the solar system would have evolved over the past four billion years.

"In coming up with an explanation for the celestial bodies, we thought it would be most natural to assume the existence of a yet unknown planet," Mukai said.

"Based on our hypothesis, we calculated how debris moved over the past four billion years. The result matched the actual movement of the celestial bodies we can observe now," he said.

He was hopeful about research by Kobe University, the University of Hawaii and Taiwan's National Central University.

"We are expecting that the ongoing joint celestial observation project will eventually discover Planet X," Mukai said."

News Source: Discovery News

A Space Probe's Problem: One Missing Comet

admin@mysteriesunsealed.com — Sat, 29 Dec 2007 18:21:08 GMT

A NASA comet probe heading back to Earth for a gravity boost will be redirected after the disappearance of its intended target.

Deep Impact, which won funding for an extended mission after its successful close-up studies of Comet Tempel 1 in 2005, was expected to use its Dec. 31 flyby of Earth for a slingshot maneuver to rendezvous with a comet known as 85P/Boethin in 2008.

Scientists spent the summer and early fall searching for the target so Deep Impact could be dispatched on the right path. A hunt by the most sophisticated telescopes on the planet, however, turned up nothing.

"We couldn't find it," University of Maryland astronomer Michael A'Hearn, who heads the Deep Impact science team, told Discovery News.

The comet had only been seen twice before, but was expected to reappear last summer. A'Hearn believes the comet escaped detection because its orbit differs from predictions. But it could have fragmented into smaller pieces or even dissipated completely during its last pass around the sun.

"Comet Linear did that in 2000, but it's quite rare. If that is the right explanation, that's really fascinating," A'Hearn said.

Scientists had a backup target, Comet Hartley 2, but reaching it would take Deep Impact an extra two years and cost another $8 million.

"That's why we were trying so hard to find Comet Boethin," A'Hearn said.

With budgets tight, it was far from assured that NASA would pick up the extra expense, but last week the U.S. space agency agreed to do so.

Deep Impact has another mission before it reaches its new target: Beginning in January, it will use the larger of its two telescopes to hunt for planets circling nearby stars. The study is funded for six months, but scientists are considering asking for an extension because Deep Impact's comet rendezvous, originally planned for late 2008, is now delayed until October 2010.

Although A'Hearn and his colleagues will have to wait longer, Comet Hartley 2 may be an even better target than Comet Boethin. While both are about the same size -- roughly a half-mile in diameter -- Hartley 2 may be more active, A'Hearn said.

The original Deep Impact mission blasted a hole into its target so instruments could study its underlying structure and composition. With no more probes to release, the follow-up study of Hartley 2 will be restricted to measurements of surface features and naturally occurring phenomena, such as ice jets.

While only a handful of comets have been studied in detail, scientists have been surprised by their physical and chemical differences.

News Source

Blast From Empty Space Poses Scientific Mystery

admin@mysteriesunsealed.com — Sat, 29 Dec 2007 18:14:47 GMT

Just when space scientists thought they had solved the mystery of the brightest explosions in the universe, along comes one that has the experts befuddled.

The confounding "gamma ray burst" was detected by space-based instruments and the Swift orbiting gamma ray observatory on Jan. 25, 2007. At first it stood out only because it was rather bright -- one of the brightest ever recorded. Since then, however, the burst -- dubbed GRB 070125 -- has proven far more interesting in other ways.

A telescope imaged the afterglow of the mysterious burst called GRB 070125 on January 26, 2007. At right, an image taken of the same field on February 16 with the Keck I telescope reveals no trace of an afterglow, or a host galaxy. The white cross in the zoom-in view marks the GRB's location. The two nearest galaxies, and their distances, are marked with arrows.

Unlike the other hundred or so similar gamma ray bursts discovered -- most of which shine out momentarily with incredible brightness from crowded stellar nurseries -- GRB 070125 appears to be all by itself in space without any signs of a galaxy around it. That goes against everything astronomers have learned about gamma ray bursts over the last ten years.

"It's out in the middle of nowhere," said gamma ray burst investigator Derek Fox of Pennsylvania State University. Fox coauthored a report on GRB 070125 that will be published in The Astrophysical Journal.

The current theory holds that gamma ray bursts like GRB 070125 are given off by super-jumbo-sized stars that run out of fuel and violently collapse to form black holes, explained Neil Gehrels, principal investigator of NASA's Swift telescope.

Such huge stars can only be created in very gas and dust-rich parts of galaxies where lots of other stars are also being born. So it makes no sense to find such a star living and dying in the empty space between galaxies. Nor is there time for such stars to travel out into intergalactic space, said Gehrels, since mega stars are also the shortest-lived.

The mystery of GRB 070125 only deepened as astronomers narrowed in on the burst's location, about 9.5 billion light-years away, with more powerful telescopes. They were still looking for the light from the galaxy which theory predicted must be there, but no galaxy appeared.

The researchers also collected the visible light from the burst's afterglow with the Gemini North 8-meter telescope in Hawaii, then split the light into its spectrum of colors to look for telltale "absorption" lines. These dark lines are sure signs of material in the burst's home galaxy filtering the light of the burst.

"We usually see very deep absorption features," said Caltech astronomer Brad Cenko, lead author of the report. "In this case we didn't see any. That in and of itself is pretty unique."

Nor did any other researchers have any luck.

"There are quite a few groups that have looked at this place," confirmed Gehrels. "You can really tell for sure that there's nothing going on there."

The next step, says Cenko, is to win some time using the Hubble Space Telescope to look for the missing galaxy. If it's not there, it's possible they could see some signs that two nearby galaxies, already observed with the Keck I telescope, have been colliding and leaving a string of lonely stars of all ages and sizes between them, he said.

"That's the leading hypothesis," Cenko said.

Then again, they could find something else entirely unexpected. As Cenko added, "There are still lots of surprises in this field."

News Source

Space probe targets third comet after second vanishes

admin@mysteriesunsealed.com — Tue, 18 Dec 2007 21:34:45 GMT

A comet targeted for a flyby with NASA's Deep Impact spacecraft cannot be found, forcing mission planners to send the probe to a different comet. The comet may have evaded telescopes simply because its predicted orbit was incorrect, or, more intriguingly, it might have disintegrated completely.

The Deep Impact spacecraft completed its main mission in 2005, when it slammed a metal impactor into comet Tempel 1 and watched the debris fly. After the successful encounter with Tempel 1, the mission team had hoped to carry out a second rendezvous, this time with a comet called 85P/Boethin, in late 2008.

But the team now says comet Boethin is nowhere to be found, forcing them to target a different comet called Hartley 2 instead.

Comet Boethin has been spotted only twice, first when it was discovered during a close approach to the Sun in 1975, and again during a second close passage in 1986.

The comet was not seen when it was expected to approach the Sun most recently in 1997. But that is not surprising since it was behind the glare of the Sun as seen from Earth that time, says Michael A'Hearn of the University of Maryland in Baltimore, US, chief scientist for the extended mission.

In October, some of the world's most powerful telescopes, including the Very Large Telescope (VLT) array in Paranal, Chile, and the Subaru observatory in Hawaii combed the skies for the comet, but failed to see it.

Crumble away

It is possible that the comet was destroyed during the 1997 Sun encounter, disintegrating from the Sun's heat, A'Hearn says. But comet Boethin never comes closer to the Sun than just beyond Earth's orbit, making it unlikely to have disintegrated, he says.

"Disappearing in the sense of breaking up and dissipating is actually very rare" for such a comet, he told New Scientist. "If it disappeared, then that is fascinating in itself – only one other comet has done that in recent memory." Comet Linear-S4 disintegrated and disappeared in 2000. A comet called 73P/Schwassmann-Wachmann 3 was seen fragmenting in 2006, but it did not crumble away to invisibility.

A somewhat more likely possibility is that the comet broke into a few large chunks that are still intact but have drifted too far from the original comet's orbit to have been spotted in searches to date, A'Hearn says.

Uncertain orbit

However, the most likely explanation of all is that telescopes have simply been searching in the wrong place, he says. Because the comet has been briefly spotted only twice, scientists have not been able to compute its path around the Sun very precisely.

Despite the uncertainty in comet Boethin's orbit, the Deep Impact team had selected it as a target because it would have been relatively quick and easy to get to, reducing the cost of the extended mission.

Now, NASA has decided to divert the spacecraft to Hartley 2 instead. Hartley 2 is about 1.6 kilometres across, about the same size as comet Boethin. Although it will take longer to get there – the encounter will not occur until 2010 – Hartley 2 is more active than Boethin was, which will give the spacecraft more to look at.

The spacecraft turned on its rocket engine for three minutes on 1 November, setting up for a flyby of Earth on 31 December, the first of three Earth encounters that will use our planet's gravity to adjust the spacecraft's trajectory for its new mission.

Pummelled by dust

The spacecraft will pass within about 1000 kilometres of the comet. Trying to get much closer than that would risk the spacecraft getting pummelled by dust particles, which can do a lot of damage due to their high speeds, A'Hearn says.

Only a small number of comets have been seen up close. Adding another to the mix will help scientists understand better which features tend to be the same and which vary from comet to comet, he adds.

The Deep Impact spacecraft's extended mission has been named EPOXI. The spacecraft will also use its camera to watch stars with so-called transiting planets – planets known to pass in front of their parent star as seen from Earth, periodically blocking some of the starlight.

The way the starlight varies as the planet moves in front of the star could lead to the discovery of rings or moons around the known planets, and possibly result in the discovery of additional planets with masses as small as three times that of Earth.

News Source

New Type of Dying Star Discovered

admin@mysteriesunsealed.com — Sat, 01 Dec 2007 23:15:33 GMT

A rare new kind of star may have been discovered. It is much like the white dwarf our own sun should eventually become—save for a mysterious shroud of carbon ash.

The findings could shed light on the life and death of stars, astronomers said.

After they exhaust all their nuclear fuel, more than 97 percent of the stars in our galaxy—virtually all with eight to 10 times the mass of our sun or less—are expected to end up as white dwarfs, remnant stars roughly the size of Earth and very dense. Our sun is predicted to become a white dwarf more than five billion years from now.

Surprise

Until now, all known white dwarfs had atmospheres rich in either hydrogen or helium. Unexpectedly, scientists now find what seems to be a new class of white dwarf, with skies made primarily of carbon and with little or no trace of hydrogen or helium.

"Nobody ever thought this could exist," astrophysicist Patrick Dufour at University of Arizona at Tucson told SPACE.com. "It will be a challenge to explain how they form."

Roughly 80 percent of all white dwarfs had until now been thought to possess hydrogen-rich atmospheres, with the rest having helium-rich atmospheres. These new carbon-rich white dwarfs seem to be quite rare in comparison, making up at most less than one-thousandth of all white dwarfs.

So far, based off observations at Apache Point Observatory in New Mexico, the researchers have found eight such white dwarfs. "There are certainly more," Dufour said.

The scientists detailed their findings in the Nov. 22 issue of the journal Nature.

Dying embers

All white dwarfs form after stars lose up to 85 percent of their mass in their death throes. Perhaps during this phase, a few white dwarfs might lose "practically all of their hydrogen and helium," Dufour said.

"As a result, we see the underlying core of the star where there used to be nuclear reactions," he explained. "The carbon we are seeing are thus the 'ashes' of the burning of helium that once took place in the core of the star."

White dwarfs evolve from stars not massive enough to explode as supernovas upon their deaths. The researchers suggest the carbon-rich white dwarfs are born from stars near this limit, eight to 10 solar masses large.

To learn more about these mysterious new white dwarfs, Dufour and his colleagues plan to focus on the eight they have found so far with bigger telescopes.

"The most important implication here is in regard to stellar evolution," Dufour said. "If they are the result of the evolution of massive stars near the mass limit before exploding as supernova, they could eventually teach us a lot about how massive stars evolve and die."

News Source

Star Cluster's Extreme Speed Puzzles Astronomers

admin@mysteriesunsealed.com — Fri, 30 Nov 2007 20:00:48 GMT

A ragged company of stars is rushing through the chaotic core of our galaxy, travelling faster than can easily be explained. The new measurement of its orbit, made with the 10-metre Keck telescope in Hawaii, US, also deepens a mystery surrounding the Milky Way's central black hole.

The Arches cluster is a group of young stars only about 100 light years from the very centre of the galaxy, a dangerous region where strong gravitational fields can tear a star cluster apart. "The Arches will only survive 10 or 20 million years," says Andrea Stolte of the University of California in Los Angeles, US.

Stolte is a member of the team that has now tracked the cluster's trajectory. They took one image of the cluster in 2002 using the 8-metre Very Large Telescope (VLT) in northern Chile, and then another in 2006 using Keck.

They got a precise fix on the cluster using Keck's "laser guide star" system, in which a laser hits sodium atoms in the upper atmosphere to create an artificial star. By monitoring the guide star, the optics of the telescope can adapt in real time to disturbances in the atmosphere, which would otherwise blur the image.

The team found that after four years the cluster, which lies 25,000 light years away, had moved by seven millionths of a degree. That corresponds to a speed through space of more than 200 kilometres a second.

That is puzzlingly fast. The cluster is thought to have formed when two gas clouds in the inner galaxy collided – but the most likely candidate clouds are travelling much more slowly than the Arches cluster.
Freakish speeds

Perhaps the Arches is simply a freak, formed in the collision of two rare, exceptionally fast clouds? Stolte and her colleagues plan to look at another cluster in the region, called the Quintuplet, to see if it is also travelling at such an unruly pace.

The newly plotted course of the Arches also sheds some light on the innermost stars of the galaxy, which surround the monstrous black hole at the galactic centre. Many of these stars are young, only about 6 million years old, and astronomers wonder how they were able to form. Ordinary gas clouds should have been shredded by the black hole's gravity before they could condense into stars.

One theory is that the young stars were carried into the central cluster by other clusters that had formed farther out. According to recent calculations, however, most clusters are destroyed before they can get close enough. The new measurements now show that the Arches cluster, at least, can't perform such interstellar deliveries, because its orbit doesn't take it close enough to the black hole.

Another possibility is that a flock of stars could have been shepherded in by an intermediate-sized black hole about 1000 times the mass of the Sun. A more popular alternative, however, is that these unusual stars formed where they are, out of a very dense disc of gas. Under its own strong gravity, this gas could have collapsed into stars. "I think that the disc scenario is becoming increasingly likely," Stolte told.

News Source

Tiny Galactic Building Blocks Spotted

admin@mysteriesunsealed.com — Sun, 25 Nov 2007 18:38:09 GMT

Astronomers have found nine of the faintest, tiniest and most compact galaxies ever seen.